This invention relates to snubbers or shock absorbers and, more particularly, to a mechanical device for restraining portions of a power plant to withstand earthquakes while at the same time providing freedom for movement of those devices which undergo thermal expansion or contraction during use.
In recent years the increased demand for electrical power and the reduced availability of oil has resulted in a demand for the increased use of nuclear power to generate electricity. While the feasibility of nuclear power plants is not questioned, their construction has posed certain questions as to the ability of equipment such as emergency cooling lines or pipes, heat exchangers, etc., to withstand earthquakes.
Current thinking would appear to call for the cooling lines or pipes, etc., to be rigidly coupled to building structures. While this would be simple enought to accomplish, the problem is more complicated than first meets the eye.
Cooling lines generally undergo thermal expansion ranging from inches to feet during thermal heat-up and cool-down cycles. Thus some means must be provided to support cooling lines and other devices which undergo thermal expansion in a manner such that movement during thermal cycles may be easily accomplished while at the same time providing protection under dynamic conditions such as an earthquake.
In the past, power plants have generally relied upon hydraulic dampers to restrain cooling pipes. However, hydraulic dampers have come into disfavor since they leak, they generally have sealing problems in radiation environments and they have a history of high maintenance costs.
Accordingly, a new and improved snubber or restraining apparatus was needed for use in supporting power plant devices which would be totally mechanical, would contain no hydrocarbon fluids, or hydro carbon material, could sustain high temperature or nuclear radiation environments and remain operational as well as provide protection from high seismic forces while permitting expansion due to thermal cycles.
The present invention provides such an apparatus which will meet the aforementioned requirements. In addition, the present invention provides an apparatus which may be constructed without requiring the use of springs, however springs may be used if desired in some cases.